The conclusion of the study by Dohn and colleagues [1] that “oral atovaquone and intravenous pentamidine have similar rates for successful treatment of mild and moderate P. carinii pneumonia” is misleading. More treatment failures were noted (29% compared with 17%) and more deaths (13% compared with 8%) occurred in patients treated with atovaquone than in those treated with pentamidine. Although the observed differences in this small study did not reach statistical significance, they are consistent with those obtained in a larger study showing the inferiority of atovaquone compared with trimethoprim-sulfamethoxazole, which is probably therapeutically equivalent to pentamidine [2, 3]. Because the authors discontinued enrollment prematurely, it is inappropriate for them to conclude that they have proved the null hypothesis, that is, that the two treatments do not differ. Atovaquone may be well tolerated, but the available data suggest that it is less effective than either pentamidine or trimethoprim-sulfamethoxazole. Reasonable alternatives for treatment of P. carinii pneumonia in patients with a history of intolerance to trimethoprim-sulfamethoxazole include, in addition to pentamidine, trimethoprim-dapsone, clindamycin-primaquine, and rechallenge or desensitization (or both) with trimethoprim-sulfamethoxazole [4, 5].